Modern vehicles, especially automobiles, increasingly use systems and sensors for detecting and gathering information about the vehicle's surroundings. Autonomous vehicles can use such information for performing autonomous, partially autonomous, and driver assistance driving and/or parking operations. Many autonomous, semi-autonomous, and driver assistance driving and/or parking operations rely on cooperation from a multitude of sensors including cameras, LiDAR sensors, and ultrasonic sensors, among others. The data from one or more of the sensors can be used to map the environment. This mapping can be used to determine whether the space in the direction of navigation is unoccupied (e.g., free-space) or occupied by objects or hazards (e.g., vehicles, walls, pedestrians, potholes, etc.). Knowledge of the environment can allow for an autonomous or partially autonomous vehicle to navigate without colliding with objects or other hazards.
LiDAR sensors can be particularly useful for mapping the environment (e.g., by generating a three-dimensional point cloud) because laser range measurements are particularly accurate and can be generated with reasonable speed required for autonomous or partial autonomous operations. Conventionally, LiDAR data can be processed using height thresholding, where objects can be classified as objects/hazards based on their height relative to the vehicle ground. However, even with a well calibrated setup (with a known geometric relationship between LiDAR sensor coordinates and vehicle coordinates, and which can be eventually extended further into a real-world coordinate system), conventional techniques such as height thresholding cannot reliably differentiate between ground/free space and objects/hazards due to real-world environmental conditions including the fluctuation of LiDAR coordinate system cause by dynamic motion of the vehicle during navigation and non-flat driving surfaces roads (varying slopes, pots holes, dips, speed bumps, etc.). Improved processing to distinguish between free space and objects/hazards is required.